1. Field of the Invention
The present invention relates to a method for manufacturing a silicon carbide semiconductor device, and particularly to a method for manufacturing a silicon carbide semiconductor device having heat treatment.
2. Description of the Background Art
Most of general semiconductor manufacturing apparatuses for mass production are adapted to large-sized silicon substrates based on the specifications standardized in the field of a semiconductor, and they are normally designed to handle substrates having a size not smaller than approximately 150 mm (6 inches). Meanwhile, industrially, a high-quality single crystal silicon carbide substrate has a size not greater than approximately 100 mm (4 inches). Then, in order to adapt a silicon carbide substrate to a general semiconductor manufacturing apparatus, it has been proposed to support a silicon carbide substrate on a support substrate greater than that. For example, according to the technique described in Japanese Patent Laying-Open No. 2000-277405, it has been proposed to provide an SiC wafer on an Si wafer.
In manufacturing a semiconductor device, heat treatment is normally required. In particular, activation heat treatment for activating an impurity introduced through ion implantation requires a high temperature. A temperature for activation heat treatment in the case of a silicon carbide substrate is significantly higher than in the case of a silicon substrate, and for example, it is around 1800° C. This temperature is high enough to melt silicon and silicon oxide. Thus, manufacturing of a semiconductor device including a silicon carbide substrate, that is, manufacturing of a silicon carbide semiconductor device, requires heat treatment at a very high temperature. When the technique described in the publication above is used for manufacturing a silicon carbide semiconductor device requiring heat treatment at a high temperature as such, an Si wafer supporting an SiC wafer cannot withstand a heat treatment temperature.